Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

872
FXUS63 KLOT 281136
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
536 AM CST Fri Nov 28 2025

.KEY MESSAGES...

- Winter Storm Warning now in effect for all but Ford, Iroquois,
  Newton, Jasper and Benton Counties, where a winter storm watch
  remains in effect.

- Impactful snow is expected late Friday night through Saturday
  night. There is a >90% chance for 6"+ amounts and higher end
  travel impacts along and north of I-80.

- Well below normal temperatures will persist into or through
  next week, perhaps with additional chances for snow (Monday
  afternoon and night).

&&

.DISCUSSION...
Issued at 259 AM CST Fri Nov 28 2025

Through Saturday Night...

Upgraded the winter storm watch to a winter storm warning for
most of the area with increasing confidence for 6+ inches of
snow. Maintained the winter storm watch for the far southeast
cwa where snowfall amounts are expected to be less and there is
some potential for a mix/change to light rain/drizzle late
Saturday afternoon into Saturday evening.

Overall forecast reasoning remains on track with no significant
changes to the forecast this morning. Light snow is expected to
spread across northern IL late tonight/early Saturday morning
with light snow falling across much of northern IL, north of
I-80 by the predawn hours. The snow will then increase in
intensity Saturday morning with the heaviest snow falling during
the afternoon and then slowly tapering off in intensity from
southwest to northeast Saturday evening. The snow will likely
end completely early Sunday morning with perhaps some lingering
flurries of snow showers later Sunday morning. The blended pops
are in the high chance range and this seems a bit high, but did
not make any changes. Lake effect snow showers may continue
across far northwest IN, especially Porter County with
additional snow accumulation possible and the winter storm
warning may need to be extended for Porter County for these lake
effect snow showers.

QPF amounts remain fairly steady from the models, generally
ranging from 0.9 inches in the northwest and western cwa, to
perhaps as low as 0.6 inches across the southeast cwa. Have
generally maintained the snow ratios from the previous forecast,
which for the bulk of the area may only be in the 11:1 or 10:1
range, perhaps a bit higher across the northwest cwa and a bit
lower across the far southeast cwa. Combining these brings storm
total amounts for much of the warning areas into the 6-10 inch
range. Its possible areas where the watch remains in effect
could reach 6 inches, but confidence is too low to upgrade those
areas at this time. For areas northwest of an Ottawa to Aurora
to Waukegan line, snow totals may be more in the 10 to possibly
12 inch range and a separate segment may eventually be needed
but for now have just highlighted locally higher amounts for
those areas. The track of the low will also need to be watched
closely. Any north shift to the low track could have some large
impacts on snow amounts.

Snowfall rates will likely be in the one inch range for several
hours Saturday afternoon with some potential for a few hours of
rates of 1-2 inches an hour, especially across northwest IL. cms

Sunday through Thursday:
Issued at 301 PM CST Thu Nov 27 2025

A 1035-1040 hPa high building into the Great Plains impinging
on the low over Lake Huron and Georgian Bay on Sunday will
induce strong gradient winds and a modest 3-5mb/3hr pressure
rise over much of the area. Some shallow blowing and drifting
snow will likely persist for open areas conditional on a drier
character of the expected snow pack. Will include patchy
blowing snow in the forecast for now, with the greatest concerns
on N/S-oriented roadways in open areas west of the Fox River
Valley. Additionally, ongoing strong CAA with shallow stratus
under a steadily lowering subsidence will support some lingering
light snow showers or flurries well into the day Sunday. The
lower inversion will also limit lake effect snow intensity near
the lake in northwest Indiana, but additional minor
accumulations are probable for northeast Porter County.

The inversion should lower enough to erode remaining stratus
Sunday night as the surface ridge edges toward the area. As long
as stratus does not persist well into the night, diminishing
winds with a fresh snow pack will promote a rather chilly Sunday
night with lows potentially at or below zero across interior
northern Illinois. Very cold conditions will persist through
Tuesday as a reinforcing shot of colder air arrives on Monday.

A mid-level wave crossing the Ohio River Valley late Monday
afternoon and Monday night is now exhibiting decent phasing with
a sub-tropical system over the Lower Mississippi River Valley,
which supports increasing chances for light accumulating snow to
affect at least the southern CWA during this time. Resultant
higher cloud cover would ultimately tamper very cold conditions
Monday night, but if there is any clearing, sub-zero lows will
again be possible.

Deep troughing now anchored over eastern Canada will lead to
colder conditions through the remainder of the week, with some
energy from a Pacific NW trough bringing another period of
potential snow to the western Great Lakes Wednesday into
Thursday.

Kluber

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 536 AM CST Fri Nov 28 2025

Widespread snow is expected to move into the terminals late
tonight, with conditions likely deteriorating to LIFR/VLIFR in
accumulating snow Saturday morning/midday.

Quiet VFR weather conditions will remain in place across the
forecast area through this evening. Breezy west-northwest winds
will persist this morning with a few sporadic gusts near 20 kt
possible, though winds will generally be decreasing through the
day as surface high pressure builds in from the west. Winds
should become light/variable by evening and light southeast
overnight.

A mid-level disturbance currently moving ashore across the
Pacific Northwest is forecast to lead to surface low pressure
development across the Plains later today/tonight. This low is
then expected to track northeast into the western Great Lakes
region through Saturday night. Widespread light snow is expected
to develop in advance of this system tonight, then intensify
across the area Saturday morning and persist through Saturday
night before tapering off early Sunday. Confidence is somewhat
low on exact start time tonight, as there will be some low-level
dry air to overcome, but the expectation is that snow will
develop near/after midnight and become moderate to heavy by
mid-late Saturday morning. Current TAFs thus depict a
deterioration in conditions with vsbys 1-2SM by daybreak and
eventually less than 1SM by late morning/midday Saturday.
LIFR/VLIFR conditions will most likely persist beyond the end of
the current ORD/MDW 30 hour TAF period Saturday
afternoon/evening. Southeast winds will increase into the 10-15
kt range Saturday morning, with some gusts 20-25 kts possible
toward and beyond midday.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Storm Warning from 3 AM Saturday to 6 AM CST Sunday for
     ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ103-ILZ104-
     ILZ105-ILZ106-ILZ107-ILZ108.

     Winter Storm Watch from late tonight through late Saturday
     night for ILZ033-ILZ039.

IN...Winter Storm Warning from 3 AM Saturday to 6 AM CST Sunday for
     INZ001-INZ002.

     Winter Storm Watch from late tonight through late Saturday
     night for INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 9 AM CST this morning for the IL
     nearshore waters.

     Small Craft Advisory until 3 PM CST this afternoon for the IN
     nearshore waters.

&&

$$

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